The Collaborative International Dictionary of English v.0.48:
Stibnite \Stib"nite\, n. (Min.) A mineral of a lead-gray color and brilliant metallic luster, occurring in prismatic crystals; sulphide of antimony; -- called also antimony glance, and gray antimony. [1913 Webster]WordNet (r) 3.0 (2006):
stibnite n 1: a soft grey mineral; the chief ore of antimony